Emerging Roles of Branched-Chain Amino Acid Supplementation in Human Diseases

Abstract

The branched-chain amino acids (BCAAs), namely, valine, leucine, and isoleucine, are indispensable amino acids required for body protein synthesis. Unlike other amino acids, the BCAAs are primarily catabolised in the extrahepatic tissues. The BCAAs play role in regulation of protein synthesis and turnover as well as maintenance of the body glutamate-glutamine level. In strenuous and traumatic conditions, the BCAAs are oxidized which limits their availability in tissues. Such condition affects the body glutamate-glutamine pool and protein synthesis mechanisms. Thus BCCA supplementation is emerging as a nutritional strategy for treating many diseases. Many studies have found that BCAA administration is able to improve the health status of the patients suffering from different diseases even though there are conditions where they do not exert any effect. There are also some reports where elevated BCAAs have been shown to be associated with the pathogenesis of diseases. In this review, we have discussed the implication of BCAA supplementation in different pathological conditions and their relevant outcomes.

Therapeutic Uses of Amino Acids

“…BCAAs play vital roles in regulation of protein synthesis and maintenance of glutamate-glutamine levels in the body. BCAAs are oxidised during high-energy-demanding and stressful conditions, and as a result, limit their accessibility in body tissues, which in the long run upsets mechanisms controlling the synthesis of proteins and body glutamate-glutamine pool [6].…”

“…Several studies have reported that when BCAA supplements are administered, patients experience improvements in health, although there are some disease conditions where BCAAs showed no efects. However, increased levels of BCAAs in the body have been observed to be involved in disease pathology [6].…”

“…They are three of nine essential amino acids that are not synthesised by Amino Acid -New Insights and Roles in Plant and Animalthe human body and therefore must be obtained from diet. Approximately 35% of indispensable muscle proteins and 40% of total amino acids required by mammals are composed of these BCAAs [6]. The three BCAAs either together or with leucine alone can stimulate protein synthesis and can also inhibit protein degradation depending on the context [12].…”

“…Catabolism of these amino acids is initiated by transamination reaction with α-ketoglutarate to form glutamate and branched-chain keto acids (BCKAs). Then, the glutamate is converted to glutamine by the action of the glutamine synthetase enzyme [6]. Glutamine (Figure 5), which is derived mainly from skeletal muscles [13], is one of the most abundant amino acids in the body [14].…”

“…Some of the most prominent areas of therapeutic applications of amino acids are for treatment of brain metabolism and neurotransmission imbalances. Other areas in which amino acids also ind key applications are immune function, cardiovascular and gastrointestinal (GI) health [1], treatment of liver diseases, fatigue, skeletal muscle damage, cancer prevention, burn, trauma and sepsis, maple urine disease and diabetes [6]. Bardaweel [2] investigated the antibacterial activities of some d-amino acids, which include d-alanine, d-lysine, d-serine and d-proline (Figure 1), against Bacillus subtilis, Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa and Xanthomonas vesicatoria and reported that the amino acids exhibited relatively low inhibitory efectiveness against the pathogens.…”